How to fix relationship lines?
As you said you've tried Ctrl+p, so the door is not a child of any object.
Then the only thing that can cause this problem is that the origin far away from the door. Select the door, press T > on left hand side menu set "Origin to Geometry". 

If it still doesn't work, share the blender file with us or recreate the problem (if you can) in a separate project and share that file.